From acquaintances that knew Katsuyama personally, he was described as a genius marketer, not a technologist. Before even Lewis came along, he had crafted a large part of this narrative: the Thor matching technology succeeded on a compelling story. Lewis got sucked in.
The personal reactions you may have seen (William O'Brian on CNBC) are authentic: HFT participants (and those who deal with them) have been villified in an industry already viewed in a negative light. There are some bad apples, but there are also many who genuinely believe that they are doing a service for the market.
I don't blame Lewis for this. I just hope that there is an author that can create a compelling story that doesnt fall for the tired trope of the evil HFT trader. The story exists - it is just very technical and nuanced at times. Unfortunately, many HFT participants have been shamed away from standing for what they believe in so there are very few left to tell the story.
If you want to read a rebuttal and learn more about the markets at the same time, check out this analysis by Larry Tabb - a market research consultant prominent in the US execution technology market: http://www.scribd.com/doc/215693938/No-Michael-Lewis